Implications For Cancer Development Research Articles

Identification of BAP1-associated MicroRNAs and Implications in Cancer Development

Having role in gene regulation and silencing, miRNAs have been implicated in development and progression of a number of diseases, including cancer. Herein, I present potential miRNAs associated with BAP1 gene identified using in-silico tools such as TargetScan and Exiqon miRNA Target Prediction. I identified fifteen highly conserved miRNA (hsa-miR-423-5p, hsa-miR-3184-5p, hsa-miR-4319, hsa-miR125b-5p, hsa-miR-125a-5p, hsa-miR-6893-3p, hsa-miR-200b-3p, hsa-miR-200c-3p, hsa-miR-505-3p.1, hsa-miR-429, hsa-miR-370-3p, hsa-miR-125a-5p, hsa-miR-141-3p, hsa-miR-200a-3p, and hsa-miR-429) associated with BAP1 gene. We also predicted the differential regulation of these twelve miRNAs in different cancer types.

Sphingomyelin Plays a Critical Role in Membrane-Related Effects Induced by the Steroid Saponin Ginsenoside Rh2

Cholesterol (Chol) and sphingomyelin (SM) are known to cluster into transient nanometric domains, forming a liquid ordered (Lo) phase. These domains serve as a platform that contributes to cellular signaling including cell survival or proliferation with potential implications in cancer development. Saponins, amphiphilic compounds widely found in plants, attract more and more attention based on their biological activities including anticancer properties. Although the activity for most saponins (e.g. digitonin, α-hederin) is usually attributed to their interactions with membrane Chol, our recent publication showed that Chol, contrary to SM, delays the cytotoxicity of the saponin ginsenoside Rh2 in human cancer cell lines (A549, THP-1, and U937)[1], renewing the idea that saponin activity is only ascribed to an interaction with Chol. In this study, we elucidated the respective importance of Chol and SM in the membrane-related effects of Rh2 using a large panel of biophysical approaches while carefully modulating their lipid compositions, i.e. the presence or absence of Chol or SM. Using lipid monolayers, we observed that Rh2 preferentially interacted with eSM:ePC, then eSM:ePC:Chol followed by ePC:Chol. Using Large Unilamellar Vesicles (LUVs), we found that Rh2 increased the vesicle size, decreased membrane fluidity and induced membrane permeability with the same ranking, i.e eSM:ePC>eSM:ePC:Chol>ePC:Chol. Using Giant Unilamellar Vesicles (GUVs), Rh2 generated positive curvature in SM-containing membrane and small buds followed by intra-luminal vesicles in the absence of SM. Altogether, our results indicate that SM promotes and accelerates membrane-related effects induced by Rh2. To the best of our knowledge, this study is the first to reveal the critical role of SM in membrane-related effects induced by a saponin reconsidering the theory that Chol is the only responsible for the activity of saponins. [1] Toxicol Appl Pharmacol 352, 59-67(2018).

TGF beta promotes repair of bulky DNA damage through increased ERCC1/XPF and ERCC1/XPA interaction.

Transforming growth factor beta (TGFβ) is multifunctional cytokine that is involved in the coordination and regulation of many cellular homeostatic processes. Compromised TGFβ activity has been attributed to promotion of human cancers. Recent studies have identified a role for TGFβ in response to radiation-induced DNA damage, suggesting a link between TGFβ and the DNA damage response with implications for cancer development. In this study, the effects of TGFβ on promoting the repair of bulky DNA damage, through modulation of nucleotide excision repair (NER), were investigated. We show that treatment of cells with exogenous TGFβ leads to enhanced repair of DNA damage formed by polycyclic aromatic hydrocarbons and ultraviolet-C radiation; similarly, cells with constitutively activated endogenous TGFβ signaling show comparable responses. This effect of TGFβ is independent of the cell cycle. The response to TGFβ is decreased in cells that have compromised TGFβ signaling through RNA interference of Smad4 and is decreased in NER-deficient cells and cells with compromised NER through RNA interference of excision repair cross-complementing group 1 (ERCC1). Increased interaction and nuclear localization of ERCC1/xeroderma pigmentosum (XP) F and ERCC1/XPA proteins is observed after TGFβ treatment. Our study represents the first experimental evidence of a role for TGFβ in the repair of bulky DNA damage resulting from promotion of the interaction and localization of repair protein complexes involved in the incision step of NER.

Detours to Replication: Functions of Specialized DNA Polymerases during Oncogene-induced Replication Stress.

Incomplete and low-fidelity genome duplication contribute to genomic instability and cancer development. Difficult-to-Replicate Sequences, or DiToRS, are natural impediments in the genome that require specialized DNA polymerases and repair pathways to complete and maintain faithful DNA synthesis. DiToRS include non B-DNA secondary structures formed by repetitive sequences, for example within chromosomal fragile sites and telomeres, which inhibit DNA replication under endogenous stress conditions. Oncogene activation alters DNA replication dynamics and creates oncogenic replication stress, resulting in persistent activation of the DNA damage and replication stress responses, cell cycle arrest, and cell death. The response to oncogenic replication stress is highly complex and must be tightly regulated to prevent mutations and tumorigenesis. In this review, we summarize types of known DiToRS and the experimental evidence supporting replication inhibition, with a focus on the specialized DNA polymerases utilized to cope with these obstacles. In addition, we discuss different causes of oncogenic replication stress and its impact on DiToRS stability. We highlight recent findings regarding the regulation of DNA polymerases during oncogenic replication stress and the implications for cancer development.

Targeting ubiquitin-proteasome pathway by natural, in particular polyphenols, anticancer agents: Lessons learned from clinical trials

The ubiquitin-proteasome pathway (UPP) is the main non-lysosomal proteolytic system responsible for degradation of most intracellular proteins, specifically damaged and regulatory proteins. The UPP is implicated in all aspects of the cellular metabolic networks including physiological or pathological conditions. Alterations in the components of the UPP can lead to stabilization of oncoproteins or augmented degradation of tumour suppressor favouring cancer appearance and progression. Polyphenols are natural compounds that can modulate proteasome activity or the expression of proteasome subunits. All together and due to the pleiotropic functions of UPP, there is a great interest in this proteasome system as a promising therapeutic target for the development of novel anti-cancer drugs. In the present review, the main features of the UPP and its implication in cancer development and progression are described, highlighting the importance of bioactive polyphenols that target the UPP as potential anti-cancer agents.

Interactions between the circadian clock and TGF-β signaling pathway in zebrafish.

BackgroundTGF-β signaling is a cellular pathway that functions in most cells and has been shown to play a role in multiple processes, such as the immune response, cell differentiation and proliferation. Recent evidence suggests a possible interaction between TGF-β signaling and the molecular circadian oscillator. The current study aims to characterize this interaction in the zebrafish at the molecular and behavioral levels, taking advantage of the early development of a functional circadian clock and the availability of light-entrainable clock-containing cell lines.ResultsSmad3a, a TGF-β signaling-related gene, exhibited a circadian expression pattern throughout the brain of zebrafish larvae. Both pharmacological inhibition and indirect activation of TGF-β signaling in zebrafish Pac-2 cells caused a concentration dependent disruption of rhythmic promoter activity of the core clock gene Per1b. Inhibition of TGF-β signaling in intact zebrafish larvae caused a phase delay in the rhythmic expression of Per1b mRNA. TGF-β inhibition also reversibly disrupted, phase delayed and increased the period of circadian rhythms of locomotor activity in zebrafish larvae.ConclusionsThe current research provides evidence for an interaction between the TGF-β signaling pathway and the circadian clock system at the molecular and behavioral levels, and points to the importance of TGF-β signaling for normal circadian clock function. Future examination of this interaction should contribute to a better understanding of its underlying mechanisms and its influence on a variety of cellular processes including the cell cycle, with possible implications for cancer development and progression.

Human papillomavirus type 16 E5-mediated upregulation of Met in human keratinocytes

Human papillomaviruses (HPVs) cause benign lesions that can lead to malignancy. How cellular changes induced by viral oncogenes contribute to the progeny virion production is not always clear. Stromally-derived growth factors and their receptors are critical for development of malignancy, but their impact on the pre-malignant HPV life cycle is unknown. We show that HPV16 increases levels of Met, a growth factor receptor critical for tumor cell invasion, motility, and cancer metastasis. The viral oncogene E5 is primarily responsible for Met upregulation, with E6 playing a minor role. Met induction by E5 requires the epidermal growth factor receptor, which is also increased by E5 at the mRNA level. E5-induced Met contributes motility of HPV-containing cells. Finally, Met signaling is necessary for viral gene expression, particularly in the differentiation-dependent phase of the viral life cycle. These studies show a new role for E5 in epithelial-stromal interactions, with implications for cancer development.

Telomeres: Implications for Cancer Development.

Telomeres facilitate the protection of natural ends of chromosomes from constitutive exposure to the DNA damage response (DDR). This is most likely achieved by a lariat structure that hides the linear telomeric DNA through protein-protein and protein-DNA interactions. The telomere shortening associated with DNA replication in the absence of a compensatory mechanism culminates in unmasked telomeres. Then, the subsequent activation of the DDR will define the fate of cells according to the functionality of cell cycle checkpoints. Dysfunctional telomeres can suppress cancer development by engaging replicative senescence or apoptotic pathways, but they can also promote tumour initiation. Studies in telomere dynamics and karyotype analysis underpin telomere crisis as a key event driving genomic instability. Significant attainment of telomerase or alternative lengthening of telomeres (ALT)-pathway to maintain telomere length may be permissive and required for clonal evolution of genomically-unstable cells during progression to malignancy. We summarise current knowledge of the role of telomeres in the maintenance of chromosomal stability and carcinogenesis.

Carnitine palmitoyltransferase 1C regulates cancer cell senescence through mitochondria-associated metabolic reprograming.

Cellular senescence is a fundamental biological process that has profound implications in cancer development and therapeutics, but the underlying mechanisms remain elusive. Here we show that carnitine palmitoyltransferase 1C (CPT1C), an enzyme that catalyzes carnitinylation of fatty acids for transport into mitochondria for β-oxidation, plays a major role in the regulation of cancer cell senescence through mitochondria-associated metabolic reprograming. Metabolomics analysis suggested alterations in mitochondria activity, as revealed by the marked decrease in acylcarnitines in senescent human pancreatic carcinoma PANC-1 cells, indicating low CPT1C activity. Direct analyses of mRNA and protein show that CPT1C is significantly reduced in senescent cells. Furthermore, abnormal mitochondrial function was observed in senescent PANC-1 cells, leading to lower cell survival under metabolic stress and suppressed tumorigenesis in a mouse xenograft model. Knock-down of CPT1C in PANC-1 cells induced mitochondrial dysfunction, caused senescence-like growth suppression and cellular senescence, suppressed cell survival under metabolic stress, and inhibited tumorigenesis in vivo. Further, CPT1C knock-down suppressed xenograft tumor growth in situ. Silencing of CPT1C in five other tumor cell lines also caused cellular senescence. On the contrary, gain-of-function of CPT1C reversed PANC-1 cell senescence and enhanced mitochondrial function. This study identifies CPT1C as a novel biomarker and key regulator of cancer cell senescence through mitochondria-associated metabolic reprograming, and suggests that inhibition of CPT1C may represent a new therapeutic strategy for cancer treatment through induction of tumor senescence.

Novel Insights into Gastric Cancer: Methylation of R-spondins and Regulation of LGR5 by SP1.

Recently, it was shown that leucine-rich repeat-containing receptor 5 (LGR5)-expressing stem cells are the cellular origin of intestinal-type gastric cancer. The aim of our study was to uncover regulatory mechanisms of LGR5 expression in gastric mucosa and their implications for cancer development. Reporter assays identified an LGR5 promoter fragment, which is highly relevant for active LGR5 expression. Chromatin immunoprecipitation verified that SP1 is bound within this region, and reporter activity increased in SP1 transfected cells. Subsequently, the expression of R-spondins (RSPO1 and RSPO2), ligands of LGR5, was explored in neoplastic and nonneoplastic gastric tissue and gastric cancer cell lines. Using IHC, distinct spatial expression patterns of LGR5, RSPO1, and RSPO2 were found in nonneoplastic stomach mucosa and gastric cancer. RSPO expression was lower in gastric cancer compared with nonneoplastic mucosa on both the transcriptional (P = 0.003 for RSPO1 and P = 0.000 for RSPO2; n = 50) and the translational level. Methylation-specific PCR showed higher methylation levels of RSPO1/2 and reexpression of RSPOs in the gastric cancer cell lines MKN45 and MKN74 were induced by demethylating 5-aza-C treatment. Finally, expression patterns of LGR5 and RSPO were similar in gastric cancer.Implications: This report identifies a regulatory mechanism of LGR5 expression in gastric carcinogenesis, with SP1 as an important component of the transcriptional complex and LGR5 activity, which is modulated by its ligands RSPO1 and RSPO2, whose expression is modulated by methylation.Visual Overview: http://mcr.aacrjournals.org/content/15/6/776/F1.large.jpg. Mol Cancer Res; 15(6); 776-85. ©2017 AACR.

Relevance of necroptosis in cancer.

Resistance to caspase-dependent apoptosis is often responsible for treatment failures in cancer. Finding novel therapeutic strategies that can activate alternative cell death programs appears to be appealing. Necroptosis is a form of programmed necrosis that occurs under caspase-deficient conditions. This alternative form of cell death has recently emerged as a potential anticancer therapy that could overcome apoptosis resistance. A growing understanding of the molecular events triggering necroptosis helped to examine its implication in cancer development and to define new therapeutic strategies. Genetic and proteomic analysis suggest that necroptosis is deregulated in many cancers. Various preclinical and clinical compounds induced necroptosis and have demonstrated significant therapeutic efficacy. Moreover, accumulating evidence has shown that necroptosis promotes anticancer immune response. A better knowledge of the cascade of events regulating necroptosis is expected to assess the feasibility of its therapeutic exploitation for cancer therapy.

Conformational Dynamics of Lysine Methyltransferase Smyd2. Insights into the Different Substrate Crevice Characteristics of Smyd2 and Smyd3.

Smyd2, the SET and MYND domain containing protein lysine methyltransferase, targets histone and nonhistone substrates. Methylation of nonhistone substrates has direct implications in cancer development and progression. Dynamic regulation of Smyd2 activity and the structural basis of broad substrate specificity still remain elusive. Herein, we report on extensive molecular dynamics simulations on a full length Smyd2 in the presence and absence of AdoMet cofactor (covering together 1.3 μs of sampling), and the accompanying conformational transitions. Additionally, dynamics of the C-terminal domain (CTD) and structural features of substrate crevices of Smyd2 and Smyd3 are compared. The CTD of Smyd2 exhibits conformational flexibility in both states. In the holo form, however, it undergoes larger hinge motions resulting in more opened configurations than the apo form, which is confined around the partially open starting X-ray configuration. AdoMet binding triggers increased elasticity of the CTD leading Smyd2 to adopt fully opened configurations, which completely exposes the substrate binding crevice. These long-range concerted motions highlight Smyd2's ability to target substrates of varying sizes. Substrate crevices of Smyd2 and Smyd3 show distinct features in terms of spatial, hydration, and electrostatic properties that emphasize their characteristic modes of substrates interaction and entry pathways for inhibitor binding. On the whole, our study shows how the elasticity and hinge motion of the CTD regulate its functional role and underpin the basis of broad substrate specificity of Smyd2. We also highlight the specific structural principles that guide substrate and inhibitor binding to Smyd2 and Smyd3.

Altered primary chromatin structures and their implications in cancer development.

Cancer development is a complex process involving both genetic and epigenetic changes. Genetic changes in oncogenes and tumor-suppressor genes are generally considered as primary causes, since these genes may directly regulate cellular growth. In addition, it has been found that changes in epigenetic factors, through mutation or altered gene expression, may contribute to cancer development. In the nucleus of eukaryotic cells DNA and histone proteins form a structure called chromatin which consists of nucleosomes that, like beads on a string, are aligned along the DNA strand. Modifications in chromatin structure are essential for cell type-specific activation or repression of gene transcription, as well as other processes such as DNA repair, DNA replication and chromosome segregation. Alterations in epigenetic factors involved in chromatin dynamics may accelerate cell cycle progression and, ultimately, result in malignant transformation. Abnormal expression of remodeler and modifier enzymes, as well as histone variants, may confer to cancer cells the ability to reprogram their genomes and to yield, maintain or exacerbate malignant hallmarks. At the end, genetic and epigenetic alterations that are encountered in cancer cells may culminate in chromatin changes that may, by altering the quantity and quality of gene expression, promote cancer development. During the last decade a vast number of studies has uncovered epigenetic abnormalities that are associated with the (anomalous) packaging and remodeling of chromatin in cancer genomes. In this review I will focus on recently published work dealing with alterations in the primary structure of chromatin resulting from imprecise arrangements of nucleosomes along DNA, and its functional implications for cancer development. The primary chromatin structure is regulated by a variety of epigenetic mechanisms that may be deregulated through gene mutations and/or gene expression alterations. In recent years, it has become evident that changes in chromatin structure may coincide with the occurrence of cancer hallmarks. The functional interrelationships between such epigenetic alterations and cancer development are just becoming manifest and, therefore, the oncology community should continue to explore the molecular mechanisms governing the primary chromatin structure, both in normal andin cancer cells, in order to improve future approaches for cancer detection, prevention and therapy, as also for circumventing drug resistance.

Tolerance of Tumor-Specific T cells in Melanoma Metastases.

Tolerance of Tumor-Specific T cells in Melanoma Metastases.

Posttranscriptional methylation of transfer and ribosomal RNA in stress response pathways, cell differentiation, and cancer.

Significant advances have been made in understanding the functional roles of evolutionarily conserved chemical modifications in RNA. By focusing on cytosine-5 methylation, we will highlight the latest insight into the mechanisms how posttranscriptional methylation contributes to cell fate decisions, with implications for cancer development. Several mutations in RNA-modifying enzymes have been identified to cause complex human diseases, and linked posttranscriptional modifications to fundamental cellular processes. Distinct posttranscriptional modifications are implicated in the regulation of stem cell maintenance and cellular differentiation. The dynamic deposition of a methyl mark into noncoding RNAs modulates the adaptive cellular responses to stress and alterations of methylation levels may lead to cancer. Posttranscriptional modifications such as cytosine-5 methylation are dynamically regulated and may influence tumour development, maintenance, and progression.

The Mammalian circadian clock gene per2 modulates cell death in response to oxidative stress.

Living in the earth’s oxygenated environment forced organisms to develop strategies to cope with the damaging effects of molecular oxygen known as reactive oxygen species (ROS). Here, we show that Per2, a molecular component of the mammalian circadian clock, is involved in regulating a cell’s response to oxidative stress. Mouse embryonic fibroblasts (MEFs) containing a mutation in the Per2 gene are more resistant to cytotoxic effects mediated by ROS than wild-type cells, which is paralleled by an altered regulation of bcl-2 expression in Per2 mutant MEFs. The elevated survival rate and alteration of NADH/NAD+ ratio in the mutant cells is reversed by introduction of the wild-type Per2 gene. Interestingly, clock synchronized cells display a time dependent sensitivity to paraquat, a ROS inducing agent. Our observations indicate that the circadian clock is involved in regulating the fate of a cell to survive or to die in response to oxidative stress, which could have implications for cancer development and the aging process.

Abstract 5359: TGFβ promotes the DNA damage response and repair of DNA damage induced by benzo[a]pyrene

Abstract Transforming growth factor beta (TGFβ) is involved in coordinating a number of cellular processes including proliferation, differentiation and apoptosis, and as such, dysregulation of TGFβ signalling has significant implications for cancer development. TGFβ is rapidly and persistently activated in response to irradiation-induced DNA damage (Barcellos-Hoff et al, J Clin Invest 1994; 93:892-9) and has been implicated in regulation of the irradiation-induced DNA damage response (Kirshner et al, Cancer Res 2006; 66:10861-9). We have recently published two studies investigating the activation of DNA damage signalling in cells after exposure to two highly potent polycyclic aromatic hydrocarbons (PAHs), benzo[a]pyrene (BP) and dibenzo[a,l]pyrene (DBP) (Niziolek-Kierecka et al, Chem Res Toxicol 2012; 25:862-72 and Jarvis et al, Toxicol Appl Pharmacol 2013; 266: 408-18). The aim of this study was therefore to investigate a potential role for TGFβ in the response to PAH-induced DNA damage. Using human hepatocellular carcinoma cells (HepG2) we studied activation of DNA damage signalling by Western blotting. Formation of γH2AX and ATM foci was assessed by immunofluorescence and DNA damage levels were quantified by Comet assay. HepG2 cells were exposed to non-cytotoxic concentrations of BP and DBP (confirmed by MTT assay). Exposure to BP or DBP caused a concentration- and time-dependent increase in DNA damage signalling assessed by phosphorylation of Chk1, H2AX and p53. DBP was approximately 60-fold more potent at inducing prolonged DNA damage signalling than BP. Prolonged γH2AX and ATM foci were observed after exposure to 1 µM BP or 50 nM DBP for 48 hours consistent with persistent DNA damage whereas exposure to 0.1 µM BP or 5 nM DBP caused a transient increase in foci up to 24h and lower levels at 48h suggesting repair. To investigate the role of TGFβ signalling in repair of PAH-induced DNA damage, exogenous TGFβ (1 ng/ml) was added during incubation with BP and DBP. Addition of TGFβ significantly decreased the number of γH2AX and ATM foci in cells exposed to either BP or DBP and this was consistent with a decrease in DNA damage. Levels of both damage foci and Comet tail moments were similar to control levels suggesting activation of DNA repair in response to addition of TGFβ. Exposure to BP or DBP with or without TGFβ caused an increase in Smad2 phosphorylation confirming activation of TGFβ signalling. Smad2 activation was more pronounced after exposure to BP compared to DBP and RNA interference experiments are ongoing to further elucidate the mechanism of PAH induction of TGFβ signalling. Taken together our data suggest an important role for TGFβ signalling in repair of PAH-induced DNA damage. Furthermore, our data suggest a possible link between compromised TGFβ signalling and persistent DNA damage that might have important implications in understanding PAH-induced carcinogenesis. Citation Format: Ian WH Jarvis, Kristian Dreij, Ulla Stenius. TGFβ promotes the DNA damage response and repair of DNA damage induced by benzo[a]pyrene. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5359. doi:10.1158/1538-7445.AM2014-5359

9: The ATM-mediated DNA damage response: Implications for cancer development and treatment

9: The ATM-mediated DNA damage response: Implications for cancer development and treatment

DNA crosslinking damage and cancer - a tale of friend and foe.

Interstrand crosslinks (ICLs) represent a major challenge for DNA replication and transcription by preventing DNA strand separation. Cells deficient in ICL repair are hypersensitive to a variety of bifunctional alkylating agents and exhibit excessive genomic instability. Patients with deficient ICL repair, such as those with Fanconi anemia, are predisposed to a broad spectrum of cancers. The profound cellular toxicity of ICLs is exploited clinically in cancer chemotherapy. Therefore, understanding the mechanism of ICL repair and its impact on cancer development and treatment is very important. Studies of diseases with defective ICL repair, especially Fanconi anemia, have revealed unique ICL repair mechanisms in humans. In this review, we describe pathways and factors involved in ICL damage response and their implications in cancer development and treatment.

Abstract 3592: Roles of miR-199a-5p and COX-2 in arsenic-induced tumor angiogenesis.

Abstract Arsenic is a well-known human carcinogen which is closely associated with lung cancer. However, the mechanism underlying the arsenic-induced carcinogenesis remains to be elucidated. The alterations of miRNAs profiles in cancers have profound implication in cancer development. However, it remains to be determined whether the alterations of miRNA signature in response to carcinogens such as arsenic may result in cell malignant transformation and tumor growth. In this study, we developed an in vitro model by transforming human lung epithelial BEAS-2B cells through long-term exposure to low concentration of arsenic. The BEAS-2B cells were malignantly transformed validated by cell proliferation, anchorage independent growth and tumor growth assay. By utilizing this model, we found that miR-199a-5p expression level was dramatically repressed in arsenic-transformed cells. Re-expression of miR-199a-5p impaired arsenic-induced tumor angiogenesis through directly targeting hypoxia inducible factor-1α (HIF-1α). Interestingly, we found another proangiogenic factor cyclooxygenase-2 (COX-2) that was also upregulated in arsenic-transformed cells and was predicted as a target of miR-199a-5p. It was confirmed by generating COX-2 3’UTR miRNA luciferase reporters with wild-type or mutant binding sites with miR-199a-5p. Overexpression of miR-199a-5p inhibited COX-2 protein expression. Functional study revealed that knockdown of COX-2 by siRNA in arsenic-transformed cells decreased tumor angiogenesis. We further showed that the COX-2 promoter contains a functional hypoxia response element (HRE). HIF-1α regulated COX-2 expression at the transcriptional level via direct binding to the HRE (-576/-584) located within the COX-2 promoter. Thus, arsenic-induced COX-2 activation is mediated by repression of miR-199a-5p and activation of HIF-1. Moreover, prostaglandin E2 (PGE2), a product of COX-2 regulated HIF-1 expression in a positive-feedback manner. In addition, arsenic-transformed cells have high levels of reactive oxygen species (ROS) for activating COX-2 pathway. Taken together, our results demonstrate that arsenic-induced angiogenesis through miR-199a-5p repression and pro-inflammatory responses induced by ROS. Both pathways lead to activation of HIF-1/COX-2 pathway. These findings establish critical roles of miR-199a-5p and its downstream targets HIF-1/COX-2 in arsenic-induced tumor angiogenesis. As miR-199a-5p is generally downregulated, whereas COX-2 is overexpressed in human lung cancer tissues, they may be used as new therapeutic targets for lung cancer treatment in the future. Citation Format: Jun He, Richard Carpenter, Yue Jiang, Qing Xu, Bing-Hua Jiang. Roles of miR-199a-5p and COX-2 in arsenic-induced tumor angiogenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3592. doi:10.1158/1538-7445.AM2013-3592